A recent reading in Manhattan at the Strand bookstore by David Sedaris, whose most recent book is “When You Are Engulfed in Flames,” may have offered a glimpse of the future. A man named Marty who had waited in the book-signing line presented his Kindle, on the back of which Mr. Sedaris, in mock horror, wrote, “This bespells doom.” (The signed Kindle was photographed, but its owner’s full name is unknown.)Asked if she had any inkling if the practice of having Kindles signed is common, a spokeswoman for the online bookseller Amazon.com, which makes the device, declined to respond, but it has been happening at least intermittently for more than a year. (...) Mr. Sedaris wrote in a recent e-mail message that he has actually signed “at least five” Kindles, and “a fair number of iPods as well, these for audio book listeners.” A frequent chronicler of his own eccentricities, the author often encounters his readers’ quirks at the book-signing table.“The strangest thing I’ve signed is a woman’s artificial leg,” Mr. Sedaris continued in his e-mail message. “Last year in Austin I signed an actual leg, and its owner had my signature tattooed into her flesh. The night before that, a nursing mother offered me a taste of her pre-pumped breast milk, and I took her up on it.”